Detection Of Nitroaromatic Explosives Research Articles

Thienothiophene based AIE-Active bulky materials for sensitive explosive detection

Sensors for selective and sensitive detection of nitroaromatic (NAC) explosives are of current interest for both national security and environmental protection. In this work, three thienothiophene based AIE active materials (TPE2-TT, TPE3-TT and TPE3-TPA-TT), possessing tetraphenylethylene and triphenylamine units, were designed and synthesized as chemosensors for sensitively detecting 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (DNT) and trinitrophenol (TNP) explosives. Among the AIEgens, TPE3-TT demonstrated a maximum Stern-Volmer constant (Ksv) reaching to 2.9 x 104 M−1 by quenching response toward TNP. They exhibited vivid visual quenching on absorbent papers. Moreover, probe-explosive complex interactions and their mechanisms were investigated using density functional theory (DFT). Their remarkable properties indicated that TT based AIEgens are promising probes for sensitively detecting the explosives, which provided a new source of potential leading to new designs for detection of explosives.

Regulation on the ligand fluorescence in UiO-66-Y metal-organic frameworks for effective detection of nitro-aromatic explosives

Rapid, sensitive and highly selective detection of nitro-aromatic explosives (NAEs) has become one of the most pressing environmental and safety issues. Metal-organic frameworks (MOFs) offer new possibilities for the development of new photoactive materials with excellent sensing properties. In this paper, three robust UiO-66-type fluorescent MOFs were prepared from the self-assembly of yttrium cations (Y3+) and linear dicarboxylic acid ligands, named terephthalic acid (BDC), 2-hydroxyterephthalic acid (OHBDC) and 2,5-dihydroxyterephthalic acid (DHBDC). The solid and solution fluorescence properties of three MOFs were successfully modulated by regulating the number of –OH functional groups from zero to two. At 370 nm excitation, Y-BDC MOF without –OH group was almost non-fluorescent, Y-OHBDC MOF with one –OH group emitted blue fluorescence, and Y-DHBDC MOF with two –OH groups emitted green fluorescence. Thanks to the suitable porous structures and stable frameworks, Y-OHBDC and Y-DHBDC MOFs both can quantificationally detect at least seven nitro-aromatic explosives (NAEs) by a fluorescence quenching process. Remarkably, the detection performance for 2,4,6-trinitrophenol (TNP) is the most outstanding with the KSV values of 8.4 × 104 M−1 and 2.1 × 105 M−1. Fast response, high sensitivity, strong anti-interference ability and good reusability make UiO-66-Y MOFs potential fluorescent sensors for TNP.

In-Line Thermal Desorption and Dielectric Barrier Discharge Ionization for Rapid Mass Spectrometry Detection of Explosives.

Thermal desorption (TD) of wipe-based samples was coupled with an in-line dielectric barrier discharge ionization (DBDI) source and rugged compact time-of-flight mass spectrometer (MS) for the detection of explosives, propellants, and postblast debris. The chromatography-free TD-DBDI-MS platform enabled rapid and sensitive detection of organic nitramine, nitrate ester, and nitroaromatic explosives as well as black powder and black powder substitute propellants. Parametric investigations characterized the response to TD temperature and optimized DBDI voltage, aerodynamically assisted entrainment, and fragmentation through in-source collision induced dissociation (isCID). Excess nitrate generated by the DBDI source yielded predominantly nitrate-adduct formation. Subnanogram sensitivities were demonstrated for all explosives investigated, except for nitroglycerin, specifically due to its volatility. Further, most analytes/explosives exhibited tens of picograms sensitivities. The platform also demonstrated the detection of propellant and military explosives from postblast debris. The TD-DBDI-MS system performed well without the need for aerodynamically assisted entrainment (and the associated rough pump), which along with requiring no additional gases (i.e., N2 or He) or solvents, aid in potential field deployment. The ease of TD-DBDI attachment and removal added trace solid or liquid residue detection to the rugged mass spectrometer, designed primarily for the analysis of volatile organic and inorganic compounds.

Sr(II) based one-dimensional coordination polymer as an efficient optical sensor for the detection of nitroaromatic explosives in aqueous medium

The detection of explosive materials holds significant importance due to their profound impact on various aspects such as environmental and biological systems, homeland security, and forensic investigations. Metal-organic frameworks (MOFs) and coordination polymers (CPs) have emerged as promising candidates for the selective and sensitive detection of small molecules. In this study, we synthesized a novel oxydiacetic acid functionalized strontium (II) coordination polymer, termed SDGA, using a cost-effective method known as the gel diffusion technique. The crystal structure, characterization, thermal stability, and photoluminescence properties of SDGA were thoroughly investigated by using single crystal X-ray diffraction, FTIR, UV–visible, TG/DTG, and fluorescence spectroscopy. The results revealed that SDGA crystallizes in a monoclinic crystal system with the P21/c space group. SDGA exhibits an emission peak at 340 nm under an excitation wavelength of 301 nm, attributed to the inter-ligand n-π* transition. Leveraging this photoluminescence behaviour, sensing experiments were conducted to detect nitrobenzene and p-nitrophenol within a concentration range of 0-10−20 M. The results indicate a decrease in fluorescence intensity with increasing concentrations of nitrobenzene and p-nitrophenol, indicative of a ‘turn-off’ mechanism.

Fluorescent Carbon Nitride Nanoparticles for Picric Acid Sensing.

Detection of nitroaromatic explosives is essential in the area of environmental safety. Fluorescent carbon nitride nanoparticles is a promising material for this purpose. Herein, we have prepared fluorescent carbon nitride nanoparticles (CNNPs) by one step thermal treatment of formamide. These fluorescent CNNPs is sensitive towards picric acid (PA) than other analytes both in aqueous medium and on test paper which is witnessed by fluorescence quenching based on inner filter effect (IFE). The PA detection with the fluorescent CNNPs is observed in the concentration ranges, 0 µM to 60 µM with linear range of 10 nM to 25 µM. The minimum detection limit in aqueous medium and solid phase are determined to be 26.20 nM and 10 µM respectively. Finally, the fluorescent CNNPs is applied for detection of PA in real water samples. The recoveries are in the ranges from 99.54 to 116.35% with relative standard deviation less than 3.85%. This proposed fluorescent method can act as suitable analytical technique to monitored PA concentration in water samples.

Ultrasensitive and On‐Site Detection of Nitroaromatic Explosives Through a Dual‐Mode Hydrogel Sensor Utilizing Portable Devices

AbstractThe development of straightforward and dependable explosive sensors for on‐site identification is essential to preserving public safety concerns and lowering the safety risks related to explosions. However, one of the main barriers to the advancement of on‐site explosives detection in the future is the complexity of detection process. Here, a flexible hydrogel‐based sensing platform based on 3,4‐bis (4‐(1,2,2‐triphenylvinyl) phenyl) thiophene (TPE‐Z) and a methyl red design concept is shown that simultaneously achieves all targeted properties, including being quick, portable, reliable, and resistant to external interference. This composite fluorescent probe demonstrates outstanding detection capabilities, including low detection limits (0.48 mg L−1) and rapid response times (<5 s), which can be combined with smartphones for on‐site 2,4,6‐trinitrophenol (picric acid, PA) detection. Two independent fluorescence and colorimetric channels on the sensor showed selective response to PA under fluorescence and visible light irradiation, respectively. Meanwhile, the hydrogel sensor's distinct “turn on” and “turn off” response modes to PA can be utilized to construct “YES” and “NO” logic gates, which subsequently proves that they can be employed to differentiate PA on‐site. This sensing platform based on hydrogel is envisaged to offer in‐depth insights in advancing the on‐site detection of nitroaromatic explosives.

Aggregation-induced emission enhancement (AIEE) active bispyrene-based fluorescent probe: “turn-off” fluorescence for the detection of nitroaromatics

The detection of nitroaromatic explosives in real samples is essential for environmental monitoring because of their strongly powerful nature and wide applications in industries. Aggregation-induced emission enhancement (AIEE) active fluorescent probe has been widely employed to detect nitroaromatic explosives. Hereby, a simple V-shaped bispyrene-based fluorescent probe (called py-o) with AIEE properties was designed and synthesized, which was fully charactered by 1D NMR, ESI, FTIR, and 2D NOESY spectra. The py-o displayed bright blue-green fluorescence excimer emission at 480 nm in DMF/H2O (v/v 1:1). It is observed that the fluorescence excimer emission of py-o at 480 nm was quenched by PA in solution with a quenching constant of 5.45 × 104 M–1, and the limit of detection was approximately 0.139 μM. The details of the sensing mechanism were explained using 1H NMR titrations, Job’s plot and Bensi-Hildebrand methods, which revealed a 1:1 binding ratio via the π-π interactions between PA and py-o. Meanwhile, it exhibited outstanding anti-interference ability in the detection of PA when interfering analytes were added under the same conditions. Furthermore, low-cost thin-layer chromatography (TLC) plates coated with py-o were developed as fluorescent tools for naked-eye detection of PA in the solid state. Therefore, this work provides a new method for constructing an AIEE fluorescent probe for the detection of nitroaromatic explosives to utilize in environmental monitoring.

Synthesis of High-Fluorescent Diphenyl-anthracene Derivatives and Application in Detection of Nitroaromatic Explosives and Fingerprint Identification.

The development of high-intensity fluorescent materials is always the focuses and forefront projects because of their important applications in displays, sensing and detection fields. In recent years, the detection of explosives has attracted increasing attention due to security and counterterrorism issues. Herein, two diphenyl-anthracene (DPA) derivatives were designed and synthesized by introducing strong electron withdrawing fluorine atoms and cyano-groups to DPA, which exhibited strong fluorescence both in the solution and solid phase with the absolute quantum yields up to 70.4 % and 45.9 % respectively. The detection behavior of nitroaromatic explosives such as picric acid (PA), 2,4,6-trinitrotoluene (TNT) and 3-Nitropropionic acid (3-NP) also shows good sensitivity with the quenching constant as high as 6.3×104 L mol-1 . Theoretical calculation demonstrates that the fluorescence quenching behavior of the two DPA derivatives is caused by the behavior of photoinduced electron transfer (PET) and the resonance energy transfer (RET) studies explained the higher sensitivity and selectivity of both compounds towards PA than other nitro-containing explosives. Furthermore, the strong solid-state fluorescence of the DPA derivatives also shows excellent advantages in enhancing latent fingerprint recognition.

Anthracene and porphyrin-based conjugated microporous polymer for nitrofuran antibiotics and nitroaromatic explosives detection

Given the growing threat of antibiotic pollutants to the natural environment and human health, detecting nitrofuran antibiotics rapidly, selectively, and at trace levels is crucial but presents a challenging task. In this work, we synthesized a novel luminescent conjugated microporous polymer (AP-CMP) through the polycondensation of 9,10-bis(4-formylphenyl) anthracene with pyrrole to form porphyrinic linkages. The designed porphyrin-formed reaction successfully prevents unfavorable quenching due to the aggregation and π-π stacking of highly conjugated anthracene building blocks. The as-formed highly extended and conjugated structure endows AP-CMP with high fluorescence, porosity, and the ability to selectively and rapidly detect nitrofuran antibiotics through fluorescence quenching. AP-CMP has low detection limits of 0.62 ppm for Nitrofurazone (NFZ), 0.67 ppm for Nitrofurantoin (NFT), and 0.77 ppm for Furazolidone (FZD). Furthermore, owing to its inherent electron-donating capabilities, AP-CMP has remarkable ability to identify 2,4,6-trinitrophenol from other nitroaromatic compounds via a turn-off response with a 0.2 ppm limit of detection (LOD). With its anti-interference features, high stability, reusability, metal-free nature, and potential for large-scale production, AP-CMP provides a promising dual-functional sensor platform for practical applications.

One-Dimensional Coordinated Polymers of Tetraphenylethene Pyridine and Copper-Iodide for Fluorescence Detection of Nitroaromatic Explosives.

The spatial arrangement of molecules plays a crucial role in determining the macroscopic properties of functional materials. Coordinated polymers (CPs) formed by self-assembly of organic isomeric ligands and metals offer unique performance characteristics. In this study, we present the investigation of a one-dimensional CP, named CIT-E, composed of tetraphenylethene pyridine derivative (TPE-2by-2-E) ligands and cuprous iodide. The resulting CP exhibits a one-dimensional bead chain structure with exceptional thermal and chemical stability. By leveraging the competitive absorption between CIT-E and the explosive analog 2,4-dinitroaniline, we achieve detection of the explosive through changes in the absorption intensity of the excitation light source and subsequent fluorescence response. The CP demonstrates high selectivity and anti-interference ability in detecting 2,4-dinitroaniline in aqueous solution, with a detection linear range of 0.1 μM to 300 μM and a detection limit of 0.05 μM, surpassing the national third-level emission standard. These findings highlight the potential of CP CIT-E as a promising material for the detection of explosive nitroaromatic compounds.

Aerobic direct arylation polycondensation of N-perylenyl phenoxazine-based fluorescent conjugated polymers for highly sensitive and selective TNT explosives detection

The rapid response, sensitivity, and selectivity detection of nitroaromatic explosives are major concerns for global sustainable development in order to promptly prevent and monitor their harmful effects on the environment and human health. Several different methods based on different principles have been developed to trace the nitroaromatic compound such as the 2,4,6-trinitrotoluene (TNT) compound. Recently, explosive detecting sensors based on organic conjugated fluorescent materials have been one of the most emerging subjects due to their reliable detection methods as well as portable lightweight instruments. This work uses two novel red fluorescent conjugated polymers, poly(PHP-alt-3HT) and poly(PHP-r-3HT-r-BTz), based on N-peryleneyl phenoxazine (PHP) and 3-hexyl thiophene (3HT), and benzotriazole (BTz) was successfully synthesized via an aerobic condition by direct arylation polycondensation. The red-fluorescent chemosensor based on novel conjugated polymers performed a high sensitivity for TNT detection with fast response time and good selectivity compared to common interferences. Besides tracing of TNT in the solution phase, the polymers also reached significant fluorescence quenching in the solid state by testing on a paper strip with the detection of up to 10−12 M concentrations of TNT. Further, the TNT vapor detection experiment is also effective with the fluorescence changes after only 1 min.

Design of a versatile and selective electrochemical sensor based on dummy molecularly imprinted PEDOT/laser-induced graphene for nitroaromatic explosives detection

Considering the formidable explosive power and human carcinogenicity of nitroaromatic explosives, the implementation of an accurate and sensitive detection technology is imperative for ensuring public safety and monitoring post-blast environmental contamination. In the present work, a versatile and selective electrochemical sensor based on dummy molecularly imprinted poly (3,4-ethylenedioxythiophene)/laser-induced graphene (MIPEDOT/LIG) was successfully developed and the specific detection of multiple nitroaromatic explosives was realized in the single sensor. The accessible and nontoxic trimesic acid (TMA) and superior 3, 4-ethylenedioxythiophene (EDOT) were selected as the dummy-template and the functional monomer, respectively. The interaction between the functional monomer and the template, and the morphology, electrochemical properties and detection performance of the sensor were comprehensively investigated by ultraviolet–visible spectroscopy, Fourier-transform infrared spectroscopy, scanning electron microscopy, cyclic voltammetry, and differential pulse voltammetry. Benefiting from the alliance of TMA and EDOT, the MIPEDOT/LIG sensor manifested outstanding selectivity and sensitivity for 2,4,6-trinitrotolueen (TNT), 2,4,6-trinitrophenol (TNP), 2,4-dinitrotoluene (DNT), 1,3,5-trinitrobenzene (TNB), 2,4-dinitrophenol (DNP), and 1,3-dinitrobenzene (DNB) (representative nitroaromatic explosives) with limits of determination of 1.95 ppb, 3.06 ppb, 2.49 ppb, 1.67 ppb, 1.94 ppb, and 4.56 ppb, respectively. The sensor also exhibited extraordinary reliability and convenience for environmental sample detection. Therefore, a perfect combination of versatility and selectivity in the MIPEDOT/LIG sensor was achieved. The findings of this work provide a new direction for the development of multi-target electrochemical sensors using a versatile dummy template for explosives detection.

Polycyclic aromatic‐based fluorescent probes: Color properties and fluorimetric detection of nitroaromatic explosives

AbstractDetection of nitroaromatic explosives (NAEs) is very important in terms of national security as well as the damage they cause to living things and the environment. The precision detection of these is a very important issue to reduce their harmful effects and take the necessary precautions. Electron‐rich polyaromatic fluorescent materials are highly sensitive and selective in the detection of NAEs in terms of their fluorometric quenching abilities. Three imine compounds (A‐C) containing pyrene, anthracene or naphthalene moieties were prepared and used as fluorescent probes for fluorescence detection of NAEs. The sensing abilities of materials characterized by traditional methods were investigated. The quenching‐increasing constant Ksv was calculated by using the Stern‐Volmer plot obtained from the interaction of materials with nitroaromatic. Limits of detection (LOD) values were calculated for the compounds using these data. While the quenching effect of nitro aromatic compounds was expected on fluorescent materials, increased emission was observed due to aggregation. Compound A was sensitive to Picric acid thanks to lowest LOD (38.59 μM), while compounds B and C nitrobenzene thanks to lowest LOD value (22.32 and 36.93 μM, respectively). In addition, color measurements (CIE standards) and color temperature (CCT) of the compounds were calculated.

Application of aza-BODIPY as a Nitroaromatic Sensor.

Nitroaromatic explosive detection with high sensitivity and selectivity is requisite for civilian and military safety and the ecosystem. In this study, aza boron dipyrromethene (aza-BODIPY) dye was selected as a fluorescent-based chemosensor against nitroaromatic compounds (NACs) including 2,4,6-trinitrophenol (picric acid, TNP), 2,4,6-trinitrotoluene (TNT), and 2,4-dinitrotoluene (DNT). This dye molecule exhibits sharp fluorescent behavior with high quantum yields beyond the near-infrared region (NIR) and is considered as a potential candidate for the detection of NACs. O'Shea's approach was used to synthesize tetraphenyl-conjugated aza-BODIPY molecules. Quenching of fluorescence emission of aza-BODIPY at 668 nm after the exposure to NACs was investigated under acetonitrile-water and acetonitrile-ethanol solvent conditions. The quenching responses and its mechanism were examined by considering the Stern-Volmer relationship Stern-Volmer constants (Ksv) for TNP (in water), TNP (in ethanol), TNT, and DNT, which are predicted to be 1420, 1215, 1364, and 968 M-1, respectively, all of which are sufficiently above the limit of detection (LOD) values. Thus, the present study opens up the possibility of the usage of aza-BODIPY molecules as a low-cost, light-weight sensor for the detection of NAC explosives.

New fluorescent reporters capable of Ultra-sensitively detecting trinitrotoluene on surfaces: A proof-of-concept for finding hidden nitroaromatics in the workroom

We describe the proof of concept of a portable testing setup for the detection of trinitrotoluene (TNT), a common component in hidden explosive devices. The system allows for field-testing and generation of real-time results to test for TNT traces in surfaces by simply using a filter paper and a fluorescent reporter. In this way, the controlled trapping and detection of the analyte by a chemical sensor gives reliable results at extremely low concentrations of TNT on surfaces under real life conditions suitable for daily use in ordinary sampling for example at airlines luggage storage or sport locker rooms. The reported fluorescent methodology is very sensitive and selective, allowing for the trapping and detection of TNT by a fluorescent reporter to give reliable results at very low concentrations. As a complement, we report the preparation of a modified Sylgard film that is useful under real conditions for qualitative fluorescent detection of hidden traces of TNT on surfaces or fingers by a swab method. The combination of quantitative and qualitative detection of TNT traces on surfaces constitutes a comprehensive new method for the detection of hidden nitroaromatic explosives in the workplace.

Detection of Nitroaromatic and Peroxide-Based Explosives with Amine- and Phosphine-Functionalized Diketopyrrolopyrroles.

Effective strategies for the detection and identification of explosives are highly desirable. Herein, we illustrate the efficient optoelectronic detection of nitroaromatic and peroxide-based explosives using amine- and phosphine-substituted diketopyrrolopyrroles. Selective quenching and an unprecedented enhancement of thin-film emission in the presence of nitroaromatic vapors are demonstrated via the judicious choice of amine substituents. The modulation of fluorescence emission in each case is shown to be dominated by electronic and thermodynamic effects, the vapor pressure of explosives, and the thin-film morphology. For peroxide detection, we describe an approach exploiting redox-mediated functional group transformation. The rapid oxidation of triphenylphosphine to phosphine oxide with hydrogen peroxide affords a significant increase in fluorescence emission, facilitating the sensitive turn-on detection of an important class of explosives at ppb concentrations.

Regulating donor-acceptor system toward highly efficient dual-state emission for sensitive response of nitroaromatic explosives

Dual-state emission luminogens (DSEgens) as fluorophores emit efficiently in solution and solid forms have gained increasing concern in the field of chemical sensing. Recent efforts by our group led to the identification of DSEgens as an easy-to-visualize nitroaromatic explosives (NAEs) detection platform. However, none of the previously studied NAEs probes show effective improvement in sensitivity. Here, we designed a series of benzoxazole-based DSEgens through multiple strategies driven by theoretical calculations, revealing their improved detecting performance on NAEs. Compounds 4a-4e exhibit thermal- and photo-stability, large Stokes shift as well as sensitivity solvatochromism (except for 4a and 4b). A subtle balance between rigid conjugation and distorted conformation endows these D-A type fluorophores 4a-4e with DSE properties. Furthermore, 4d and 4e show aggregation-induced emission phenomenon caused by distorted molecular conformation and restricted intramolecular rotation. Interestingly, DSEgen 4e displays anti-interference and sensitivity towards NAEs with a detection limit of 10-8 M. It can be applied for expedient and distinct visual identification of NAEs not only in solution but also on filter paper and film, supporting this new DSEgen as reliable NAEs chemoprobe.

Visual, customizable wood-based colorimetric test paper encapsulated with fluorescent carbon dots for rapid explosive detection

Wood research has recently enjoyed a renaissance due to its emerging application in various fields. This is due to the natural reaction platform and hierarchical porous structure of wood, which allows it to combine perfectly with functional materials, especially nanoscale materials. Here, we report a portable fluorescent wood (FW) test paper based on the combination of wood and carbon dots (CDs) for rapid identification and detection of nitroaromatic explosives. Thereinto, the CDs optimize the assembly of wood and open up new functions, and the naturally porous structure of wood provides grid management for CDs, effectively avoiding the accumulation of CDs. Meanwhile, the CDs are immobilized in the wood skeleton via the multiple-blockades, and the fluorescence intensity is unaffected even under harsh environmental conditions, which ensures the FW test paper exhibits high sensitivity and selectivity for trinitrophenol. The quenching reached 100% by dropping 80 μM trinitrophenol with the ultrathin FW test paper (1 × 1 × 0.009 cm), and it is still significant in the presence of interference. Interestingly, the detection results can be monitored in real time with the naked eye. As far as we know, this is the first report of trinitrophenol detection with FW test paper.

Pyrene, Anthracene, and Naphthalene-Based Azomethines for Fluorimetric Sensing of Nitroaromatic Compounds.

Special attention is given to the development of rapid and sensitive detection of nitroaromatic explosives for homeland security and environmental concerns. As part of our contribution to the detection of nitroaromatic explosives, fluorescent materials (A), (B) and (C) were synthesized from the reaction of 1,2-diaminocyclohexane with pyrene-1-carbaldehyde, anthracene-9-carbaldehyde and 2-hydroxy-1-naphthaldehyde, respectively. The structures of the prepared fluorescent azomethine probes were confirmed using FTIR, 1H-NMR and 13C-NMR spectroscopies. The basis of the study is the use of the synthesized materials as fluorescent probes in the photophysical and fluorescence detection of some nitroaromatic explosives. Emission increases occurred due to aggregation caused by π-π stacking in synthesized azomethines. To measure the nitroaromatic detection capabilities of fluorescence probes, fluorescence titration experiments were performed using the photoluminescence spectroscopy. It was observed that compound A containing pyrene ring provided the best emission intensity-increasing effect due to aggregation with the lowest LOD value (14.96μM) for the sensing of 4-nitrophenol. In compounds B and C, nitrobenzene with the lowest LOD (16.15μM and 23.49μM respectively) caused the most regular emission increase, followed by picric acid.

Conjugated Materials Containing Ethyl Benzoate Structure for Fluorescent Detection of Nitroaromatic Explosives

Conjugated Materials Containing Ethyl Benzoate Structure for Fluorescent Detection of Nitroaromatic Explosives